This invention relates to photosensor array devices, and more particularly to a photosensor array device in which a plurality of photosensors for picking up the image on a sending original are arranged in 1:1 dimensional relationship with the sending original with a view to dimensionally reducing and economizing the facsimile transmission system.
FIG. 1 is a longitudinal section illustrating the essential part of a conventional photosensor array device in the facsimile system. In the figure, reference numeral 1 denotes a source of light such as of a light emitting diode, 2 a sending original depicting thereon a pattern for transmission, 3 a contact fiber base having an inclined surface 3a and a bottom surface 3b which oppose the image surface of the sending original and upon which a light signal resulting from the light emitted from the light source 1, directed toward the sending original and then reflected by the image surface, is incident, 4 an optical fiber bundle buried in the base 3 and having one end exposed to the surfaces 3a and 3b and flush therewith, 5 a sandwich fiber base in intimate contact with an upper surface of the contact fiber base 3 and in which the other end portion of the optical fiber bundle 4 is buried such that the terminal surface of the fiber bundle is exposed to the upper surface of the base 5. This optical fiber bundle 4 is formed of a multiplicity of optical fibers put together in the shape of a bundle by fusion or bonding with an adhesive resin, and it is buried in the contact fiber base 3 and the sandwich fiber base 5, with the individual optical fibers extending in the longitudinal direction. Denoted by 6 is a transparent NESA electrode deposited on the upper surface of the sandwich fiber base 5, and by 7 a conductor electrode of a Cr-Au alloy deposited on the NESA electrode 6. This conductor electrode concurrently serves as a wire lead. By 8 is denoted a photoelectric conversion film which is deposited on the sandwich fiber base 5 to cover the end surface of the optical fiber bundle 4, the NESA electrode 6 and the conductor electrode 7. This photoelectric conversion film 8 is formed of a thin film of a Se-As-Te family amorphous substance which is used for a target film in an image pickup tube SATICON. Denoted by 9 is a common electrode to be used for applying a predetermined voltage to the photoelectric conversion film 8.
In the photosensor array device constructed as described above, in order to pick up the sending original 2, the image surface of the sending original 2 is brought into direct surface contact with, or to the close proximity of, the bottom surface of the contact fiber base 3 and the sending original 2 is moved in the direction of arrow. At the same time, light L emitted from the light source 1 is directed onto the image surface of the sending original 2, so that a light signal L' representing the pattern is sent to a light receiving surface 4a of the optical fiber bundle 4 to pass through the optical fiber bundle 4 and reach the photoelectric conversion film 8 at which the light signal L' is converted into an electric signal.
Another conventional photosensor array device of a construction as illustrated in the longitudinal section of FIG. 2 has a photelectric conversion unit formed directly on a contact fiber base 3 without the provision of a sandwich fiber base 5 as illustrated in FIG. 1. As compared with the FIG. 1 device, the FIG. 2 device is advantageous in that the material cost can be reduced because of removal of the base 5 and the fabrication can be simplified since alignment of the optical fiber bundles at the interface of the bases 3 and 5 is not required.
In so-called contact type linear photosensor array devices as described above, since the contact type line sensor neither enlarges nor reduces the image of the sending original 2 by use of a lens system, the resolution of the image is proportional to the size or fineness of the transparent NESA electrodes 6 cooperative with the photoelectric conversion film 8 to act as a photoelectric conversion element. As shown in FIG. 3, the resolution is determined by the number of NESA electrodes 6, each serving to convert light signals into electric signals, which can be disposed effectively beneath the photoelectric conversion film 8. In other words, the resolution is determined by a pitch P at which the multiplicity of NESA electrodes 6 are arranged in spaced relationship. To obtain a resolution of 8 lines per mm which warrants successful reproduction of a practically complete image pattern, for example, the pitch P is required to be as fine as 125 .mu.m (=1 mm.div.8). In this case, the conductor electrodes 7 are formed by photo-etching process. When the pitch P for the conductor electrodes 7 is of the order of 125 .mu.m or so as described above, the bonding of these conductor electrodes 7 to a drive circuit (not shown) becomes very difficult and often entails problems with reliability.
An improvement aimed at overcoming this difficulty has been proposed wherein the lead wires for the electrode set including the NESA electrodes 6 and conductor electrodes 7 are drawn out alternately on the opposite sides of the photoelectric conversion film 8 so that the individual conductor electrodes 7 may be arranged at a pitch P' of 250 .mu.m as illustrated in FIG. 4.
However, in the devices as shown in FIGS. 1 and 2 wherein the light from the light source 1 is irradiated onto the sending original 2 and reflected on the image surface of the sending original to produce the light signal which is passed through the optical fiber bundle 4 and received on the photoelectric conversion film 8, the following requirements are encountered:
(1) The light source 1 must be disposed in the vicinity of the base 3; and
(2) For reduction in the mass of fiber glass used, easiness of the aforementioned alignment and prevention of total reflection, the angle between the optical fiber bundle 4 in the contact fiber base 3 and the bottom surface 3b thereof should preferably approach to 90.degree..
Accordingly, the distance d from the photoelectric conversion film 8 to the end part of the base 5 or 3 has its own limit. Because of the limitation on this distance d, the device fails to offer a space for disposing a drive circuit. In making an attempt to somehow increase the area proportional to the distance d, it is conceivable that the sandwich fiber base 5 or the contact fiber base 3 could be extended as shown at phantom lines in FIG. 1 or 2. Obviously, this cannot be a practical solution.
For these reasons, the drive circuit is inevitably provided soly on one side with the conductor electrodes provided as shown in FIG. 3. Consequently, the bonding of the drive circuit poses itself as a serious problem.